It really is pretty simple.
I put an auto jack with a small block of wood on top under the rhs foot rest, this will lift the bike and unload the rear shock so that the swing arm drops to full extension, the rear wheel only needs to be just high enough to turn. You should also put a strap around the front brake lever and the throttle so that the bike can't move forward.
I have measured on the swing arm where the adjustment point is and put a small dot of white paint on the swing arm.
Underneath the swing arm where the chain would hit I stick a piece of metal 4mm thick on the swing arm with double sided tape (this is temporary, I remove when finished)
It is just a simple matter to rotate the rear wheel and check that the chain just contacts the piece of 4mm thick metal, check about every 30cm of chain. The reason the tension is checked about every 30cm of chain is that the rear sprocket can be mounted slightly off centre which would give the effect of a tight spot in the chain - always adjust the chain in the tightest position.
Remove the piece of metal used for measuring, remove the strap around the front brake.